Blood Tests for Diabetes Management: Glycolated Hemoglobin or HbA1c
A1C, also known as: HbA1c; glycohemoglobin test; glycosylated hemoglobin test.
What is it? A blood test that measures the amount of glycated hemoglobin in the bloodstream over a 120-day period. Glycated hemoglobin is produced when excess glucose attaches itself to hemoglobin (red blood cells). A high percentage of glycated hemoglobin indicates problems with long-term blood sugar control.
Why is this test performed? Instead of measuring your blood sugar at one specific point in time, the GHB or HbA1c test provides you with the "big picture" view of your average blood sugar control over a period of several months.
How frequently should this test be performed? The frequency of this test will vary by healthcare provider and the specific needs of the patient. The ADA recommends that the HbA1c be performed at least twice annually, and up to four times a year for individuals who are undergoing adjustments to treatment or failing to meet treatment goals, while the AACE recommends that people with type 2 diabetes take an A1C test at least quarterly. Patients who use insulin to control their type 1 or type 2 diabetes should have the test performed quarterly as well.
What is the "normal" range for results? In individuals without diabetes, approximately 5.5 to 9 percent of total hemoglobin is glycated (around 5 percent when measuring HbA1c). Individuals with well-controlled diabetes can achieve levels within this normal range. (1)
The American Association of Clinical Endocrinologists recommends individuals with diabetes aim for a target HbA1c level of 6.5 percent or lower, while the American Diabetes Association and the Canadian Diabetes Association suggest a goal of less than 7 percent. The CDA also says that "if achievable safely, an A1C of less than 6 percent...should be attempted." (2)
There are different laboratory methods of measuring GHB, depending on the subtype type of hemoglobin measured. If your GHB or HbA1c levels suddenly change dramatically and you can't attribute it to lifestyle or dietary factors, ask your doctor if he has changed labs or lab methods that could affect the interpretation of your test results.
What do abnormal results mean? The average total glycated hemoglobin level in people with diabetes at diagnosis is 10.9 to 15.5 percent. HbA1c levels usually range from 8 to 11.9 percent in uncontrolled diabetes. With proper treatment, and tight control techniques, people with diabetes can attain the "normal" GHB and HbA1c levels described above.
1 - Canadian Diabetes Association. The Canadian Diabetes Association 2003 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada, www.diabetes.ca/cpg2003/default.aspx (Accessed 2/8/08)
2 - Diabetes Care. ADA Standards of Medical Care in Diabetes—2007. (PDF Accessed 2/8/08).
3 - National Institutes of Health. Your Guide to Diabetes: Type 1 and Type 2: 2005, www.diabetes.niddk.nih.gov/dm/pubs/type1and2/index.htm (Accessed 2/08/08)
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Well maybe not so much a furor as a controversy. The question, bluntly put, is whether or not a single HbA1c reading should be sufficient and adequate to diagnose diabetes — and whether the conditions under which the test was conducted should have any bearing on the diagnostic or non-diagnostic value of the test. The lede from